Managing Difficulties

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 #define FOR(i,n,m) for(int i=n;i<=m;i++)
 4 //#define gc getchar()
 5 inline int read();static char buf[1000000],*pa=buf,*pb=buf;
 6 #define gc pa==pb&&(pb=(pa=buf)+fread(buf,1,1000000,stdin),pa==pb)?EOF:*pa++
 7 const int N=2010;
 8 int n,ct,ak,a[N];
 9 map<int,int> m;
10 int main()
11 {
12     int t=read();FOR(i,1,t){
13     m.clear();
14     n=read();ct=0;
15     FOR(i,0,n-1) a[i]=read();
16     m[a[0]]=1;
17     FOR(i,1,n-2)
18     {
19         FOR(j,i+1,n-1)
20         {
21             ak=2*a[i]-a[j];
22             if(ak>=0 && m.count(ak)) ct+=m[ak];
23         }
24         ++m[a[i]];
25     }
26     printf("%d\n",ct);
27     }return 0;
28 }
29
30
31 inline int read()
32 {
33     register int x(0);register char c(gc);bool bbb=1;
34     if(c=='-') {c=gc;}
35     while(c<'0'||c>'9')c=gc;
36     while(c>='0'&&c<='9')x=(x<<1)+(x<<3)+(c^48),c=gc;
37     if(bbb)return x;
38     else return -x;
39 }